Alternating Hemiplegia of Childhood

Definition

Definition of Alternating Hemiplegia of Childhood
Alternating hemiplegia of childhood (AHC) is a rare neurological disorder of uncertain etiology, which is named for the transient episodes, often referred to as attacks, of hemiplegia from which those with the disorder suffer. These hemiplegic attacks can cause anything from mild weakness to complete paralysis on one or both sides of the body, and they can vary greatly in duration. Attacks may also alternate from one side of the body to the other, or alternate between affecting one or both sides during a single attack. AHC is associated with many symptoms besides hemiplegia, and the majority of these become apparent in early infancy.

Symptoms

Symptoms of Alternating Hemiplegia of Childhood
AHC patients exhibit a wide range of symptoms in addition to hemiplegic attacks. These can be further characterized as paroxysmal and non-paroxysmal symptoms. Paroxysmal symptoms are generally associated with hemiplegic attacks and may occur suddenly with hemiplegia or on their own. Paroxysmal symptoms may last for variable amounts of time. Non-paroxysmal symptoms tend to be side effects of AHC which are present at all times, not just during episodes or attacks. Epilepsy, which is also considered a paroxysmal symptom, plays an important role in the progression and diagnosis of AHC.

Causes

Causes of Alternating Hemiplegia of Childhood
The exact cause of alternating hemiplegia of childhood is unknown. Some cases of AHC may be inherited as an autosomal dominant trait. In more serious cases symptoms may include mental impairment, balance and gait difficulties, excessive sweating, and changes in body temperature. Seizures can occur.

Diagnosis

Diagnosis of Alternating Hemiplegia of Childhood
As of 1993 only approximately 30 people with AHC had been described in scientific literature. Due to the rarity and complexity of AHC, it is not unusual for the initial diagnosis to be incorrect, or for diagnosis to be delayed for several months after the initial symptoms become apparent. The average age of diagnosis is just over 36 months. Diagnosis of AHC is not only difficult because of its rarity, but because there is no diagnostic test. Instead, there are several generally accepted criteria which define this disorder. Due to these diagnostic difficulties, it is possible that the commonness of the disease is underestimated.

The following descriptions are commonly used in the diagnosis of AHC. The initial four criteria for classifying AHC were that it begins before 18 months of age, includes attacks of both hemiplegia on either side of the body, as well as other autonomic problems such as involuntary eye movement (episodic monocular nystagmus), improper eye alignment, choreoathetosis, and sustained muscle contractions (dystonia). Finally, patients suffer from mental retardation, delayed development, and other neurological abnormalities. These diagnostic criteria were updated in 1993 to include the fact that all of these symptoms dissipate immediately upon sleeping. Diagnostic criteria were also expanded to include episodes of bilateral hemiplegia which shifted from one side of the body to the other.

Treatment

Treatment of Alternating Hemiplegia of Childhood
Drug therapy including verapamil may help to reduce the severity and duration of attacks of paralysis associated with the more serious form of alternating hemiplegia.

Prognosis

Prognosis of Alternating Hemiplegia of Childhood
Children with the benign form of alternating hemiplegia have a good prognosis. Those who experience the more severe form have a poor prognosis because intellectual and mental capacities do not respond to drug therapy, and balance and gait problems continue. Over time, walking unassisted becomes difficult or impossible.

Prevention

Prevention of Alternating Hemiplegia of Childhood
There are several drugs available for treatment, as well as management strategies for preventing and dealing with hemiplegic attacks.